Apparatus for making a tap



,Dea 4, 19,34. -|I JUDGE 1,982,736

APPARATUS FOR MAKING A TAP Original Filed NOV. 30, 1951 2 Sheets-Sheet l C@ A A A f. lvf `V i 1|IQ A A Dec. 4, 1934.

F. JUDGE APPARATUS FOR MAKING A. TAP

original Filed Nov. 50, 1951 2 sheets-sheet 2 Patented Dec. 4, 1934 Ui j 'y y t u, 1,982,736 APPARATUS Fon MAKING.` A TAP Franklin Judge, Greenfield, Mass., v'assigner to Greenfield Tap & `Die Corporation, Greenfield,

Mass., a corporation of Massachusetts Applicatin Novemberso, 1931, serial No. 573,038 Y l Rea'ewea'MayiLism w 5 claims. (C1. 11i- 1545 This invention relates to taps having successive axis of the shaft 35, which angle corresponds to cutting teeth offset axially on opposite sides of thepit'ch-of the desiredV thread on the tap T. the normal helix line. v l In the process of manufacture, the hob H isro- `In the preferred form, all ofthe teeth on one tated at a suitable cutting speed-andI the tap `T 5 land of the tap are offset on one side of the helix is simultaneouslyrotated at relatively slow speed. G0

line and all of the teeth on the next successive Consequently the teeth of the hob H form a series land of thel tap are'offset on the Opposite side. of grooves in a selectedland ofthe tap T and A tap having these defined characteristics is these grooves and the intervening` teeth are H shown and described in my prior application formed at the desiredpitch yangle by reason of 10 Serial No. 555,95l, filed August 8,1931. Q, u theugradual` axial adjustment orshifting of the 65 I My present invention relates to" an improved hob',`feffected by the helical `cani groove 33 as the method of manufacturing such taps and to imf cam34 rotates in unison with the rotation of the proved apparatus for use in such manufacture.` tap T. i My invention furtherrelates to certainarrange- Theapparatus'as thusffar described may be x ments and combinations of parts and'to certain used to produceordinary tapsl not having my 70 ordered procedure `.which will be hereinafter defalternately offset teeth. I

scribed and more particularly pointed out in th Inforderv to produce this alternate offsetting of appended claims.4 the teeth by the hobbin'g'oper'ation"r I 'modify the u e A. preferred form of apparatusadapted for carnjgroove 33 as indicated in Fig.` 2;

carrying out my improved method is shownin The portiona ofthe cam groove is used for 75 the drawings, in which producinggthe teethon the-land lfwhich teeth are i Fig. lis a plan view of portions of a tap hobbing offsetto the left with reference to the helix line P, 4machinejdesigned to produce my improvedtaps; providing clearance on the face a. Fig. 2 is a diagrammatic View illustrating the When the teeth on the land 1 havebeen hobbed operationof the machine and the detail steps andthe hobis outof contactwiththe talhthe 80 of the method; and cam'gr'oove is axially yoffset or shifted slightly to Fig; 3 is a detail view showing the application theright, as indicated at b,- thereby causing the of my improved method to the production of dies. teethf on the land l2 to beioffset to the right of :Referring to Fig. l, I have shown portions of a the'` normal helix line P, with clearance as in'- tap vbobbing machine including a spindle 10 rodicated at 12",] The lcam groove is then shifted 55 tatable in a bearing 11 and provided with agear back to produce a portion c in helical alignment 12 and chuck` or driver 13. A tap T is secured with'the portionja previously described and this in the chuck 13 and the opposite end ofthe tap portion produces the teeth of the land 3, with may be supported on a tail center 14. 1 clearance on the righthand side as indicated at c.

A hob `H is supported on a shaft or spindle 20, The cam groove is then again offset or shifted 90 rotatable in bearings 21 and 22 on a support 23 tothe right, as indicated at d, thereby producing longitudinally slidable in guide-ways in a stand the teeth of the land 4, with clearance on their 24. The spindle 20 and hob H may be rotated in left hand faces asindicated at d. any convenient manner, as by a flexible shaft 25. The cam groove 33 then drops abruptly back The stand 24 may be adjusted toward and from to its original position, after completion of the 95- the Work by any suitable mechanism, whereby a teeth on the land 4, and the partsy are promptly cut of the desired depth will be taken. returned to a relation where the cam roll 32 is An arm 26 projects outward from one end of the again located in the initial cam portion a. slide or support 23 and has a slot 28 to receive a Iam thus able to produce theelternetely Offset :'45- stud 29 mounted in a lever 30. The lever 30 teeth ShOWIl n my prior application, with all of 100 swings about a fixed Divot stud 3l and is provided the advantages therein described, by the use of with a cam roll 32 positioned in the peripheral a thread hobbing machine for regular taps. cam groove 33 of a cam 34, mounted on a counter- When `in use, the machine Operates eXaCtly' aS shaft 35. 'Ihe `shaft 35 is provided with a gear in the' pIOduCtOD Of regula!" taDS COIlSeClU-enlly 36 engaging the gear 12 previously described. the production of my specially offset taps re- 105 These gears are preferably of the same size, so quires no extra operations and involves no inthat the cam 34 makes one revolution for each creased expense. rotation of the tap T. The carrying out of my improved method is I The side Walls of the cam groove 33 are disnot necessarily dependent on the use of the ap- '55- posed at a slight helical angle relative to the paratus shown, as other mechanism may be used, 1.10

or the relative axial movement of thel hob or tap may be effected manually. Obviously, it is immaterial whether the hob or the tap is shifted, so long as relative axial movement occurs.

In Fig. 3, I have shown the relation of the parts for hobbing a die D by a hob H' .p rojecting into the lopenin'gfin the 'die. IRelative axial shifting of the 'hob andV die may 'be used toproduce relatively offset teeth in the die D inthe same manner as in the production of taps as previously described.

The invention may be applied to the production of three-land taps by hobbing oneland in a normal helix line, relatively shifting the hob and tap axially in one direction to cause the teeth of the next land t0 be offset at one side of said normal helix line, andl'then relatively shifting the hob and tap to cause the teeth of the third land to be offset at the opposite side of the normal helix line. In this case, the axial shift between the second and third lands may be the normal amount 4of shift used in two or four flute, commonly about .003, while the shift between the first Yand second lands, or between the third and irst, will `be only one-half .as

much. l

Having described my improved method or process and a form of apparatus by which the methodmay be carried out, I do not wish to be limited to the details vherein disclosed, otherwise than as set -forth in the claims, lbut what .I

claim is:- v

1. A machine for hobbing threading tools having cutting teeth disposed `in aplurality of circumierentially spaced and axially extended lands, having in combination, separate means to rotatably support the work and a hob in operative relation, automatic means to relatively move the hob and work axially during a hobbing operation to maintain a certain helix .line relation, and automatic means to relatively shift said hob .and work axially slightly out of-said rst helix line relation .after the teeth of one land have been hobbed, and to maintain said shifted relation during the bobbing of the next land., whereby the teeth on two successive lands are axiallyoffset relatively to each other.

2. A machine for hobbing threading tools having cutting teeth disposed in a plurality of circumferentially spaced and axially extended lands, having in combination., separate means to rotatably support the work and a hob in operative relation, a cam, and mechanism controlled thereby effective to move said hob' and work relatively axially during a hobbing operation, thereby maintaining said parts in a certain helix line relation vduring the hobbing of one land, said cam having certain operative portions olset to automatically produce a slight relative axial shifting of the hob and work out of said helix relation after the hobbing of the teeth of one land has been completed and before the hobbing of the rnextsuccessive land is commenced.

3.' A machine for hobbing threading tools having' cutting teeth disposed in a plurality of cirj'cumferentially spaced and axially extended lands, having in combination, separate means to rotatably support the work and a hob in operative relation,"a cam, and mechanism controlled thereby effective to move said hob and Work relatively axially during a hobbing operation, thereby maintaining said parts in a certain helix line relation vduring the hobbing of one land,

said cam having a cam groove disposed substantially `in a helical path but having the portions of said groove corresponding to certain lands slightly oiset axially out of the normal helical path of said cam, thereby automatically Islightly offsetting the teeth on said certain lands axially, relatively to the teeth on the remaining lands. `4.' A machine for hobbing threading tools having cutting teeth disposed in a plurality of circumferentially spaced and axially extended lands, having in combination, separate means to rotatably support the work and a hob in operative relation,v automatic means to vprogressively change the axial. relation ofthe hob and work during a hobbing operationto maintain aprimary helix vline relation, automatic means to effect an additional abrupt slight axial change in the relative positions of said hob and ,work between the hobbing of successive lands. of` the work, whereby the teethinsaid 'successive lands are slightly oiset relatively to each other, and means to thereafter restore the primary helix line relation.

5. A machine for hobbing threading tools having cutting teeth disposed in. a plurality of circumferentially spaced and axially extended lands, having incombination, separate means to rotatably support the work and a hob inoperative relation, means to progressively change the axial relation of the hob and workv during a hobbing operation to maintain a certain helix line relation, and automatic means to eiect successive abrupt axial changes in the relative positions of said hob and work between the hobbing 125 of successive lands of the work, whereby the teeth in successive lands are slightly offset relatively to each other, 'said additional changes in relative axial position being made alternately in opposite directions.

y FRANKLIN JUDGE. 

